The present invention is a process for separating an emulsion by electric field enhanced coalescence, where the emulsion comprises a discontinuous phase and a non-conducting continuous phase and the two phases have different dielectric constants and densities and at least one of the phases comprises a silicon containing compound or a silicon containing polymer. The emulsion is exposed to an electric field thereby effecting coalescence of the discontinuous phase into droplets of a size for effective gravitation from the continuous phase.
The use of high voltage electric fields to force the separation of oil field emulsions is a well known and accepted practice in the petroleum industry. These fields greatly speed the coalescence and separation of immiscible liquids, over conventional heat treaters and settlers using mechanical aids to coalescence.
Jarvis et al., U.S. Pat. No. 3,207,686, describe an electric dehydrator using an alternating current (AC) applied to an electrode to effect the separation of a water and crude oil dispersion containing gases. Jarvis et al. state that the continuous phase may be crude oil or other oils of relatively high resistivity.
Turner, U.S. Pat. No. 3,342,720, describes an improvement to electric treaters for treating oil-continuous dispersions to separate the oil from the dispersed phase. The improvement is described as a dispersion-treating electrode structure for such a treater and an arrangement of elements electrically insulating and stabilizing the energized electrode on an electric treater while supplying access to the insulation from the exterior of the treater.
In a processes for dehydrating crude petroleum-aqueous emulsions by effecting coalescence in an electric field, the nature of the current provided to the electrodes is considered important in determining the efficiency of the process. It is believed that an electric field created by an AC voltage source is more effective in separating relatively wet emulsions while an electric field created by a direct current (DC) source may be more effective in separating those dryer emulsions where particle size of the aqueous phase is small. Therefore apparatuses employing electrical fields having both AC and DC characteristics have been described.
Prestridge, U.S. Pat. No. 3,772,180, describes a system for generating a plurality of electric fields through which a mixture of water and oil is flowed for sequential exposure to fields as forces for coalescing droplets of the water into sizes great enough for their effective gravitation from the oil. More particularly, the invention is described as applying a form of DC voltage to an electrode system suspended in the mixture to generate the plurality of fields which will first function as a field generated by AC voltage and secondly as a field generated by DC voltage which will cause an ordered migration of dispersed water droplets relative to the electrodes.
Prestridge, U.S. Pat. No. 3,772,180, claims a process for coalescing water using the system described in Prestridge, U.S. Pat. No. 3,772,180, as discussed above.
Prestridge et al., U.S. Pat. No. 3,939,395, describe a rectified AC power supply for use in an apparatus for effecting separation of an aqueous emulsion by passing the emulsion through an electric field.
Hodgson, U.S. Pat. No. 4,054,451, describes an electric treater for separation of a water-in-oil emulsion, which utilizes both AC potential applied to electrodes as well as DC potential. A plurality of trays are provided through which the emulsion passes in series. The emulsion first passes through the tray or trays which have an AC potential applied to them, and then passes successively through trays which have a pulsed DC potential applied to them.
Prestridge et al., U.S. Pat. No. 4,308,127, describe an apparatus for reducing the aqueous phase of a liquid emulsion where the continuous phase has a low dielectric constant. In the apparatus a plurality of electric fields is arranged to progressively separate the liquid phases. The emulsions are first passed through one of the electric fields between insulated electrodes. With the breaking of the emulsion begun by the first electric field, the emulsion next flows in an electric field formed by applying an AC potential to uninsulated electrodes. The final stage is the passing of the almost completely broken emulsion through an electric field between electrodes having a DC potential which are arranged to systematically degrade their field.
Prestridge, U.S. Pat. No. 4,126,537, observes that one of the problems in using electric fields to effect separation of emulsions is centered in the fields strength. When the field begins to coalesce the dispersed drops its force upon the enlarging drops greatly increases. With the field strength constant, the enlarged drops travel in the second fluid fast enough to develop shear forces with the liquid in which they are dispersed to separate, or fragment the enlarged drops. Prestridge describes an apparatus providing a flow path for an emulsion through an electric field with a decreasing voltage gradient in the direction of the flow of the mixture along the path, thereby reducing fragmentation of the droplets by shear force. The decreasing voltage gradient is achieved by a gradual increasing of the distance between the electrodes.
The above described patents specifically address the problems associated with dehydrating crude oil and petroleum distillates in the petroleum industry. The described patents do not recognize that silicon containing compounds and silicon containing polymers represent unique materials that may exist in emulsion with other liquids and that such emulsions in which the two phases have different dielectric constants and densities may be separated by exposure to an electric field to enhance coalescence of the discontinuous phase into droplets of a size for effective gravitation from the continuous phase.